Auxetic behaviour in non-crystalline materials having star or triangular shaped perforations

Sheets made from easily available conventional non-crystalline materials which contain star or triangular shaped perforations are simulated through FE models and are shown to be capable of exhibiting auxetic behaviour, a property which may be observed for loading in both tension and compression. An attempt is made to explain this behaviour in terms of analytical models based on rotating rigid triangles and we also show that through careful choice of the shape and density of the perforations, one may control the magnitude and sign of the Poisson's ratio. All this provides an easy and cost-effective method for the manufacture of systems at any scale which can be tailor made to exhibit particular values of the Poisson's ratio (auxetic or non-auxetic) so as to fit particular practical applications. (C) 2010 Elsevier B.V. All rights reserved.